#include <mpi.h>
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv) {
const int PING_PONG_LIMIT = 10;
// Initialize the MPI environment
MPI_Init(NULL, NULL);
// Find out rank, size
int world_rank;
MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
int world_size;
MPI_Comm_size(MPI_COMM_WORLD, &world_size);
// We are assuming 2 processes for this task
if (world_size != 2) {
fprintf(stderr, "World size must be two for %s\n", argv[0]);
MPI_Abort(MPI_COMM_WORLD, 1);
}
int ping_pong_count = 0;
int partner_rank = (world_rank + 1) % 2;
while (ping_pong_count < PING_PONG_LIMIT) {
if (world_rank == ping_pong_count % 2) {
// Increment the ping pong count before you send it
ping_pong_count++;
MPI_Send(&ping_pong_count, 1, MPI_INT, partner_rank, 0, MPI_COMM_WORLD);
printf("%d sent and incremented ping_pong_count %d to %d\n",
world_rank, ping_pong_count, partner_rank);
} else {
MPI_Recv(&ping_pong_count, 1, MPI_INT, partner_rank, 0, MPI_COMM_WORLD,
MPI_STATUS_IGNORE);
printf("%d received ping_pong_count %d from %d\n",
world_rank, ping_pong_count, partner_rank);
}
}
MPI_Finalize();
}
 

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